1. Field of the Invention
This invention relates to stents, urology, and treatments for benign prostate hypertrophy or prostate cancer, as well as methods for correction of vessel occlusions.
2. Description of the Related Art
Prostate enlargement, also known as benign prostate hyperplasia or benign prostate hypertrophy, is a common affliction among older men. The condition involves swelling of the prostate. The prostate surrounds the urethra, or urinary tract, and swelling of the prostate prevents passage of urine from the bladder. Benign prostate hyperplasia is uncomfortable because it makes urination difficult or impossible. The condition is also dangerous because it can lead to infection of the bladder and kidneys, and severe cases may lead to death. Prostate cancer is also a common affliction among older men, and may lead to many of the same symptoms as benign prostate enlargement. Prostate cancer is more dangerous in that it may spread to other organs and is often fatal. Early treatment can reduce the risks of death due to prostate cancer.
Both prostate enlargement and prostate cancer can be treated with heat treatments such as hyperthermia or thermotherapy. As described in U.S. Pat. No. 5,830,179, the entirety of which is hereby incorporated by reference, a stent serves the dual purpose of acting as a heat source for the thermotherapy procedures, as well as acting to hold the urethra open after therapy to prevent blockage due to swelling and prostate tissue sloughing. A stent may be implanted as an interim solution to hold open the urethra while the patient awaits more aggressive surgery or treatment.
A stent may be implanted after hypothermia or cryosurgery to keep the urethra open while enlargement subsides. Finally, a stent may be implanted as a primary treatment. When the stent is implanted for any of these reasons, it is usually better to leave the bladder neck sphincter and the external sphincter unblocked by the stent. These sphincters control the flow of urine through the urethra, and if the stent is placed within these sphincters they will not be able to close. This would leave the patient incontinent. To ensure the proper positioning of the stent, the devices below provide several benefits including controlled release of the stent, tentative initial opening of the stent, and visualization of the bladder and prostatic urethra during placement.
McNamara, et al., Nitinol Stent For Hollow Body Conduits, U.S. Pat. No. 5,147,370 (Sep. 15, 1992), the entirety of which is hereby incorporated by reference, describes a catheter delivery system which uses a single pullwire to retain and release a stent wrapped on the distal end of a catheter. The stent must be provided with xe2x80x9cretaining meansxe2x80x9d in the form of pigtails or hooks on the stent ends capable of engaging a pullwire. The catheter must have two holes communicating into a lumen within the catheter, and the stent ends must enter the lumen through the holes. The pullwire is in the lumen, and engages the stent ends which enter the lumen. After release into the lumen, the retaining means are left to hang in the body lumen. This could lead to thrombus formation in blood vessels and undesirable deposition in urethral stents unless addition precautions are taken to avoid the complications. While materials may be developed in which the stent retaining pigtail structures are not set into the form of the stent, common stent alloys such as elgiloy, nitinol and stainless steel will take a set in the form of pigtails if deformed as suggested by McNamara.
Hillstead, Apparatus And Method For Placement Of A Stent Within A Subject Vessel, U.S. Pat. No. 4,913,141 (Apr. 3, 1990), the entirety of which is hereby incorporated by reference, discloses a stent delivery device which uses a pullwire running through the central lumen of the catheter and exiting the catheter to run over the stent ends. The stent is deployed by pulling the pullwire proximally, requiring the pullwire to course over intimal and endothelial surfaces of the body lumen to be treated. This could lead to damage of lumenal surfaces and attendant healing responses which are undesirable. Neither McNamara nor Hillstead provide a mechanism which permits retention and release of the stent with a mechanism which remains in the annular space of the stent, and do not present radially extending features such as the radially outwardly protruding pullwires or radially inwardly protruding pigtails.
The stent delivery systems described below permit placement of stents in the urethra and other body vessels. The devices are intended to deploy a shape memory stent or other resilient stent into the prostatic urethra under direct vision. The surgeons who use the stent delivery systems can easily place the stent within the prostatic urethra and make sure that the stent does not block the bladder neck sphincter.
In one embodiment, the stent is retained on the catheter with one or more retaining wires or rods which engage the stent ends. The catheter is comprised of two coaxial tubes, one inside the other, and the distal end of the stent is secured to the inner tube while the proximal end of the stent is secured to the outer tube. When both ends of the stent are secured to their respective tubes, the tubes may be rotated relative to each other to open the stent or tighten the stent. The stent may be released from the catheter by pulling the pullwires proximally out of engagement with the stent ends. The pullwire which retains the distal end of the stent may be released first, and the location of the distal end of the stent is observed. Once the distal end of the stent is located properly, the proximal end of the stent may be released from the catheter by pulling the pullwire which retains the proximal end of the stent out of engagement with the proximal end of the stent.
In another embodiment, a stent delivery device includes an inner tube and an outer tube. The inner tube has a distal end releasably connectable to the first end of the stent. The outer tube is rotatably slidable over the inner tube and has a distal end releasably connectable to the second end of the stent. In one embodiment, a sheath is provided which is slideable over the outer tube. A trigger may also be provided which is operably connected to the sheath for moving the sheath along the outer tube. In another embodiment, a belt is operably connected to the outer tube for rotating the outer tube relative to the inner tube. The stent may be releasably connectable to the first and second ends of the stent using at least one pullwire.
In accordance with a further aspect of the present invention, there is provided a stent deployment device. The device comprises a tubular body, having a proximal end and a distal end, the tubular body comprising a first and a second stent support. A hand piece is provided on the proximal end of the tubular body. A first control is provided on the hand piece, for manipulating the first stent support, and a second control is provided on the hand piece for manipulating the second stent support.
In one embodiment, the first stent support comprises an outer tubular sleeve for surrounding the stent. The first control comprises a control for proximally retracting the first stent support, to expose at least a portion of the stent. The first control may comprise a slider switch or lever, such as a trigger.
The second stent support may comprise a tubular body, which is releasably connected to at least a first end of the stent. The second control may comprise a control for rotating the second stent support. In one embodiment, the second control comprises a belt which is wrapped around the second stent support. Lateral retraction of the belt causes a commensurate rotation of the second stent support.
Preferably, the first and second stent supports are concentric tubes, and the stent deployment device further comprises a third stent support, comprising a third tube such that the third stent support forms an inner tube which carries the stent and is releasably connected to a distal end of the stent. The second stent support comprises an intermediate tube, concentrically carried by the inner tube, and releasably secured to a proximal end of the stent. The first stent support comprises an outer tube, concentrically carried by the intermediate tube, for covering the stent during transluminal positioning of the stent deployment device.
Preferably, the third stent support comprises an inside diameter which is greater than the outside diameter of an optical visualization device such as an endoscope which is releasably mounted to the stent deployment device, thereby forming an annular lumen extending distally through the tubular body. An infusion port may be provided on the hand piece, for communication with the annular lumen, to permit infusion of fluid media through the tubular body and out of the distal end thereof.
Further features and advantages of the present invention will become apparent from the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.